Tuning Electrical Conductance of MoS<sub>2</sub> Monolayers through Substitutional Doping

Gao, Hui; Suh, Joonki; Cao, Michael C.; Joe, Andrew Y.; Mujid, Fauzia; Lee, Kan-Heng; Xie, Saien; Poddar, Preeti; Lee, Jae-Ung; Kang, Kibum; Kim, Philip; Muller, David A.; Park, Jiwoong

doi:10.1021/acs.nanolett.9b05247

Cited by 113 publications

(141 citation statements)

References 39 publications

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“…[ 64 ] As the thickness of Re‐WSe 2 approaches monolayer level, the dielectric screening is reduced ultimately resulting in stronger Coulomb interaction between the donor nucleus and electron with higher E b . [ 37,54,64 ] Previous reports indeed demonstrate an increase in electron concentration in bulk Re‐WSe 2 whereas FEOL Re‐WSe 2 is monolayer in nature which further supports our hypothesis. [ 33 ] Conventional, external dopant activation techniques such as high‐temperature and laser‐annealing methods can be used to ionize deep level dopants in extrinsic 2D TMDCs.…”

Section: Figuresupporting

confidence: 89%

“…The superior tunability of optical and transport properties as a function of doping concentration and environmental stability are demonstrated in such monolayer films. [ 36–40 ] However, tight control over the doping concentration and fundamental understanding behind homogenous dopant distribution over large areas still remain a challenge.…”

Section: Figurementioning

confidence: 99%

“…We hypothesize that the observed phenomenon is a direct consequence of the large binding energy of the impurity state ( E b = 200–300 meV) which cannot be activated thermally at room temperature. [ 37,54 ] The impurity binding energy of layered materials is a strong function of the effective thickness where almost two orders of magnitude difference have been reported between bulk and monolayer 2D TMDCs by charge transition level (CTL) calculations and Keldysh formulation. [ 64 ] As the thickness of Re‐WSe 2 approaches monolayer level, the dielectric screening is reduced ultimately resulting in stronger Coulomb interaction between the donor nucleus and electron with higher E b .…”

Section: Figurementioning

confidence: 99%

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Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

et al. 2020

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Doping is the cornerstone of semiconductor technology, enabling the success of modern digital electronics. 2D transition metal dichalcogenides (TMDCs) are promising material platforms for future electronics applications where its wafer-scale synthesis and controllable doping will be a required prerequisite to drive the next technological revolution. [1-6] Successful realization of wafer-scale, electronic grade, intrinsic 2D TMDCs via common deposition methods is rapidly progressing, however, advances in scalable doping still remain in the "proof-of-concept" stage, delaying the largescale fabrication of logic circuits based on extrinsic 2D semiconductors. [7-12] Moreover, integration of 2D TMDCs with Si complementary metal-oxide-semiconductor at the back-end-of-line (BEOL) is being actively explored for diffusion barriers, liners, and thin-film-transistors to improve the overall integrated circuit performance. [13-16] However, BEOL production lines are Reliable, controlled doping of 2D transition metal dichalcogenides will enable the realization of next-generation electronic, logic-memory, and magnetic devices based on these materials. However, to date, accurate control over dopant concentration and scalability of the process remains a challenge. Here, a systematic study of scalable in situ doping of fully coalesced 2D WSe 2 films with Re atoms via metal-organic chemical vapor deposition is reported. Dopant concentrations are uniformly distributed over the substrate surface, with precisely controlled concentrations down to <0.001% Re achieved by tuning the precursor partial pressure. Moreover, the impact of doping on morphological, chemical, optical, and electronic properties of WSe 2 is elucidated with detailed experimental and theoretical examinations, confirming that the substitutional doping of Re at the W site leads to n-type behavior of WSe 2. Transport characteristics of fabricated back-gated fieldeffect-transistors are directly correlated to the dopant concentration, with degrading device performances for doping concentrations exceeding 1% of Re. The study demonstrates a viable approach to introducing true dopantlevel impurities with high precision, which can be scaled up to batch production for applications beyond digital electronics.

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Section: Figuresupporting

confidence: 89%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

et al. 2020

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“…Surprisingly, μ FE can be significantly improved by moderate doping, e.g., from 30 cm 2 V -1 s -1 at F O2 = 4 sccm (which is close to an intrinsic case), to 70 cm 2 V -1 s -1 at F O2 = 6 sccm, and a maximum value of 105 cm 2 V -1 s -1 can be achieved at F O2 = 10 sccm (Figures S17-S21, Supporting Information, for detailed electrical analysis). As the highly conductive phase of MoS 2-x O x from O S substitutional doping could be formed into MoS 2 lattice, [9,14] the electronic behavior of doped MoS 2 films could be modulated, and the sheet conductance and associated field effect mobility (μ FE ) could be enhanced with appropriate doping levels (F O2 ≤ 10 sccm) as shown in Figure 5e and Figure S22 (Supporting Information). At heavy doping levels (F O2 ≥ 20 sccm), the defects and visible damages (Figure 1g) prone to form on the MoS 2-x O x basal plane and serve as the main carrier scattering centers, thus degrading its electronic quality.…”

Section: Resultsmentioning

confidence: 99%

In Situ Oxygen Doping of Monolayer MoS₂ for Novel Electronics

Tang

Zheng

Wang

et al. 2020

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modulate their electrical, optical, and structural properties by introducing impurities for doping. [5-10] So far, the chemisorption and charge transfer through surface functionalization are effective approaches to achieve doping, but it has a relatively weak influences on band structures or improvements of electronic properties. [11,12] By contrast, substitutional doping is more stable and capable of tailoring the bandgap of 2D-TMDs without introducing in-gap states. [13-16] Such substitutional doping could be realized through replacing the host transition metal or chalcogen atoms with other elements during synthesis to form alloys such as Mo 1-x W x S 2 , MoS 2x Se 2(1-x) , and V x W y Mo 1-x-y S 2z Se 2(1-z) , etc. [17-21] Recently, oxygen doping of 2D-MoS 2 has attracted considerable research interests. Previous studies show that post treatments of intrinsic MoS 2 in air, ozone, or oxygen plasma could induce oxygen doping, evidenced from the enhanced catalytic reactivity, quenched photoluminescence, and improved electrical conductivity. [9,18,22-24] Such doping processes usually lead to oxygen substitution and oxidation as well and consequently yield highly disordered or fragmented lattice structures. In situ oxygen substitutional doping in 2D-MoS 2 with a controlled and nondestructive manner is thus highly desired to preserve its original lattice structure, but still remains challenging so far. In 2D semiconductors, doping offers an effective approach to modulate their optical and electronic properties. Here, an in situ doping of oxygen atoms in monolayer molybdenum disulfide (MoS 2) is reported during the chemical vapor deposition process. Oxygen concentrations up to 20-25% can be reliable achieved in these doped monolayers, MoS 2-x O x. These oxygen dopants are in a form of substitution of sulfur atoms in the MoS 2 lattice and can reduce the bandgap of intrinsic MoS 2 without introducing in-gap states as confirmed by photoluminescence spectroscopy and scanning tunneling spectroscopy. Field effect transistors made of monolayer MoS 2-x O x show enhanced electrical performances, such as high field-effect mobility (≈100 cm 2 V-1 s-1) and inverter gain, ultrahigh devices' on/off ratio (>10 9) and small subthreshold swing value (≈80 mV dec-1). This in situ oxygen doping technique holds great promise on developing advanced electronics based on 2D semiconductors.

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“…The 2D homojunctions can be (1) thicknessbased junctions, 22 (2) elemental doping based junctions, 5,28 (3) electrostatically doped junctions, 11,15,29,30 and (4) chemically doped junctions, in which there is surface chemical doping or substitutional doping of a region in a 2D material. 16,[31][32][33][34][35] In particular, 2D lateral pn junctions (2DJ) are useful for solar cells and photodetectors because the built-in potential created in the extended space charge region separates and drives the photogenerated e-h pairs to generate photocurrent. [25][26][27] While there are many reports of experimental studies on 2D junctions, the same is not true for theoretical studies, where the impact of low dimensionality on their electrical properties and their differences with 3D junctions (3DJs) are reported.…”

Section: Introductionmentioning

confidence: 99%